1 files changed, 15 insertions, 0 deletions
diff --git a/src/test/ui/nll/relate_tys/universe-violation.rs b/src/test/ui/nll/relate_tys/universe-violation.rs
new file mode 100644
index 000000000..c5f9d4406
--- /dev/null
+++ b/src/test/ui/nll/relate_tys/universe-violation.rs
@@ -0,0 +1,15 @@
+// Test that the NLL `relate_tys` code correctly deduces that a
+// function returning either argument CANNOT be upcast to one
+// that returns always its first argument.
+//
+// compile-flags:-Zno-leak-check
+
+fn make_it() -> fn(&'static u32) -> &'static u32 {
+    panic!()
+}
+
+fn main() {
+    let a: fn(_) -> _ = make_it();
+    let b: fn(&u32) -> &u32 = a; //~ ERROR mismatched types [E0308]
+    drop(a);
+}